Solvent based poly(urethane-urea) compositions made from drying oils have been sold for use as coatings for fabrics, plastics, wood, metal, and the like. These coating compositions offer good properties at a reasonable price. Nevertheless, there is a continued need to develop new waterborne poly(urethane-urea) coatings based on drying oils for a number of reasons including environmental and economical concerns associated with solvents.
Although various preparations of drying oil based waterborne poly(urethane-urea) compositions are known, discovery of new preparations and alternative compositions is needed to extend the mechanical properties of the polyurethane compositions.
One problem in particular that is associated with poly(urethane-urea) water dispersions is the inability of the composition to crosslink at room temperature upon drying. This is desirable because the composition's properties, such as chemical resistance and mechanical strength, are extended upon the crosslinking. Copending application U.S. Ser. No. 08/114,707, identified above, describes a technique whereby crosslinking is achieved at room temperature by including a polyalkylene ether polyol in the polymer formation. The presence of the polyalkylene ether polyol allows for chain extension upon the inclusion of an amine and subsequent crosslinking of the poly(urethane-urea) upon drying. Although this method represents a valuable advance in the art because it is a one component, crosslinkable poly(urethane-urea) composition, it would be desirable to find alternative methods of preparing crosslinkable, one-component poly(urethane-urea) compositions.